user
Task: How can the following equation be solved?

3x + 4y = 20

Answer:
assistant
The equation can be solved by isolating one of the variables (x or y), multiplying both sides by the inverse of the coefficient of that variable and then solving for the variable. 
For example, to solve for x, we first divide both sides by 4, giving 
$\frac{3x}{4} + y = \frac{20}{4}$. 
Then we multiply both sides by $\frac{4}{3}$ to get 
$3x + \frac{4 \times 4}{3}y = \frac{20 \times 4}{3}$. 
Finally, we subtract $\frac{4 \times 4}{3}y$ from both sides to get 
$3x = \frac{20 \times 4}{3} - \frac{4 \times 4}{3}y$. 
Then we divide both sides by 3 to get
$x = \frac{\frac{20 \times 4}{3} - \frac{4 \times 4}{3}y}{3}$. 
Now we have a linear equation for y, that can be solved for the value of y. 
Once we know the value of y, we can substitute it into the equation for x to calculate the value of x.